Pathological fibrotic states are clinically apparent abnormalities caused by the proliferation of fibroblasts, smooth muscle and other fibrogenic cells; and by the laying down of collagen and other extracellular elements typical of wound healing within specific tissues and organs of the body. The pathology is not only the abnormally excess formation of collagen polypeptide alpha chains, but also the critical modification using the enzyme lysyl oxidase to create cross-linkages between adjacent collagen chains and collagen molecules which is the basis of the structural stability, maturation, and strength of collagen and scar tissue in general. The cross-linking of the individual collagen alpha chains is the major contributor to the tensile strength of the cross-linked fibrils. Depending upon the location of the collagen chain formation and its cross-linking via the enzyme lysyl oxidase, the abnormalities may take form in a variety of clinically identifiable and diagnosed conditions including: lung fibrosis, atherosclerosis, keloid, liver fibrosis, scar tissue formation, diabetes, tumor development, and even post-operatively in procedures such as radial keratotomy where scar formation is counter productive to the purposes of the surgery. For more detailed information and review of the relationship between the enzyme lysyl oxidase and the creation of the pathological fibrotic state, the following publications are recommended. [Kagan et al., Arteriosclerosis 1:287-291 (1981); Chichester et al., Am. Rev. Respir. Dis. 124:709-713 (1981); Lerman et al., Circ. Res. 53:378-388 (1983); Levene et al., Brit. J. Exp. Path. 49:152-159 (1968); Kogan, L. L. and L. Katzen, Ann. Ophthal. 15:842-845 (1983); Chvapil, M., Life Sciences 16:1345-1362 (1975) Arem, A. J. and R. Misiorowski, J. Med. 7:239-248 (1976); and Knapp et al., Am. J. Pathol. 86:47-70 (1977)].
For these reasons, there has been considerable interest and research investigations into the enzymatic activity and properties of lysyl oxidase and its potential inhibition to prevent collagen chain cross-linking. It has been proposed that by preventing the oxidative deamination of lysine and hydroxylysine amino groups within the collagen alpha chains, which is the enzymatic function and specific activity of lysyl oxidase, the physical properties of the collagen scar tissue and the resulting fibrotic pathological state could be substantially reduced. Much of the original interest and research centered around the pathological defect found in Marfan's Syndrome, in which a decreased formation of cross-linkages within collagen and elastin fibers occurs. In prepared animal models, live rats fed sweet pea meal derived from the seeds of Lathyrus odoratus developed remarkably similar collagen cross-linking defects and skeletal abnormalities. The active ingredient responsible for the production of this defective cross-linking collagen fiber condition or "Lathyrism" was found to be beta-aminopropionitrile, which blocks cross-linkages in collagen and elastin fibers by inhibiting the enzyme lysyl oxidase. [Page R. C. and E. P. Benditt, Biochemistry 6:1142-1147 (1976) and Proc. Soc. Exp. Biol. Med. 124:454-459 (1967); Narayanan et al., Biochem. Biophys. Res Commun. 46:745-751 (1971)]. Until very recently, it was believed that the enzymatic activity of lysyl oxidase required the presence of both metallic copper; and a specific cofactor, pyridoxal phosphate [Murray, J. C. and C. R. Levene, Biochem. J. 167:463-467 (1977); Murray et al., Exp. Mol. Pathol. 28:301-308 (1978)]. Using this enzyme model, a number of other inhibitors of lysyl oxidase in addition to beta-aminopropionitrile were reported: Carbonyl Reagents [Harris et al., Biochem. Biophys. Acta 341:332-334 (1973); Kagan et al., Biochim. Biophys. Acta 365:223-234 (1974)]; isoniazid [Arem, A. J. and R. L. Misiorowski, J. Med. 7:239-247 (1976)]; Iproniazid [Rucker, R. B. and B. L. O'Dell, Biochim. Biophys. Acta 22:527-529 (1970)]; and dithiothreitol [Harris et al., Biochem. Biophys. Acta 341:332-334 (1973)]. More recently, an investigation of lysyl oxidase inhibition revealed that this enzyme in the presence of copper ion and the bound carbonyl cofactor was also inhibited by disulfhydryls, sulfhydryl-amines, and penicillamine in an irreversible manner. In addition, reversible inhibition was reported using dithiothreitol, 1,3-dithio-2-propanol, and 1,3-diaminopropane [Misiorowski, R. L. and N. J. Werner, Biochem. Biophys. Res. Comm. 85:809-814 (1978)].
Within the last few years, however, it was recognized that the lysyl oxidase enzyme cofactor was not, as previously believed, pyridoxal phosphate - but instead was pyrroloquinoline quinone (hereafter "PQQ") [Williamson et al., J. Biol. Chem. 261:16302-16305 (1986); Kagan et al., 1st International Symposium On PQQ And Quinoproteins, Delft, The Netherlands, Sept. 5-7, 1988, page 57; and Kagan, H. M., Abstract, International Congress On Elastin: Chemical And A Biological Aspects, Universita Della Basilicata, Potenza, Italy, Oct. 10-13, 1988]. This in turn has generated increased interest within the relevant components of the scientific community concerning the mode of action of the previously reported inhibitors of lysyl oxidase. In addition, because many of the previously reported compositions were not suitable for clinical and/or therapeutic use in living humans, there remains a long standing and continuing need for compositions which are effective inhibitors of lysyl oxidase in-situ, be it for human or for animal therapeutic use.